dm writecache: commit just one block, not a full page

Some architectures have pages larger than 4k and committing a full
page causes needless overhead.

Fix this by writing a single block when committing the superblock.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 01c3f51f4270436e030883311c30899d9eed1680..e18bbfd3289bf95f7f03b9453bea3250c5717780 100644 (file)
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -532,11 +532,7 @@ static void ssd_commit_superblock(struct dm_writecache *wc)
 
        region.bdev = wc->ssd_dev->bdev;
        region.sector = 0;
-       region.count = PAGE_SIZE >> SECTOR_SHIFT;
-
-       if (unlikely(region.sector + region.count > wc->metadata_sectors))
-               region.count = wc->metadata_sectors - region.sector;
-
+       region.count = wc->block_size >> SECTOR_SHIFT;
        region.sector += wc->start_sector;
 
        req.bi_op = REQ_OP_WRITE;